The present invention relates to methods and materials for making and patterning organic electroluminescent devices as well as to organic electroluminescent devices so made and to displays employing organic electroluminescent devices.
Many miniature electronic and optical devices are formed using layers of different materials stacked on each other. These layers are often patterned to produce the devices. Examples of such devices include optical displays in which each pixel is formed in a patterned array, optical waveguide structures for telecommunication devices, and metal-insulator-metal stacks for semiconductor-based devices.
A conventional method for making these devices includes forming one or more layers on a receptor substrate and patterning the layers simultaneously or sequentially to form the device. In many cases, multiple deposition and patterning steps are required to prepare the ultimate device structure. For example, the preparation of optical displays may require the separate formation of red, green, and blue pixels. Although some layers may be commonly deposited for each of these types of pixels, at least some layers must be separately formed and often separately patterned. Patterning of the layers is often performed by photolithographic techniques that include, for example, covering a layer with a photoresist, patterning the photoresist using a mask, removing a portion of the photoresist to expose the underlying layer according to the pattern, and then etching the exposed layer.
In some applications, it may be difficult or impractical to produce devices using conventional photolithographic patterning. For example, the number of patterning steps may be too large for practical manufacture of the device. In addition, wet processing steps in conventional photolithographic patterning may adversely affect integrity, interfacial characteristics, and/or electrical or optical properties of the previously deposited layers. It is conceivable that many potentially advantageous device constructions, designs, layouts, and materials are impractical because of the limitations of conventional photolithographic patterning. There is a need for new methods of forming these devices with a reduced number of processing steps, particularly wet processing steps. In at least some instances, this may allow for the construction of devices with more reliability and more complexity.
The present invention provides new thermal transfer donor elements and methods of patterning using thermal transfer donor elements. The donors and methods of the present invention are particularly suited to patterning solvent-coated materials on the same substrate as solvent-susceptible materials. This can be especially useful in constructing organic electroluminescent displays and devices as well as components for organic electroluminescent displays and devices.
In one aspect, the present invention provides a method for making an organic electroluminescent device that includes the step of thermally transferring a light emitting polymer layer and a small molecule layer from one or more thermal transfer donor elements to a receptor so that the light emitting polymer layer and the small molecule layer are disposed between an anode and a cathode on the receptor.
In another aspect, the present invention provides a thermal transfer donor element for use in making organic electroluminescent devices that includes, in the following order, a substrate, a light-to-heat conversion layer, an interlayer, and a thermal transfer layer that has, in the following order, a release layer, a cathode layer, a light emitting polymer layer, a small molecule hole transport layer, and an anode layer.
In another aspect, the present invention provides a method for patterning a first material and a second material on a receptor, which method includes selectively thermal transferring the first material proximate to the second material on the receptor from a first donor element, the first material being formed on the donor element by solution coating using a solvent, the second material being incompatible with the solvent used to coat the first material, wherein at least one of the first and second materials is an organic electroluminescent material, an organic conductor, or an organic semiconductor.
In another aspect, the present invention provides a method for patterning materials that includes forming a donor element that has a substrate and a multicomponent thermal transfer layer, the thermal transfer layer having at least a first layer that includes a solvent-coated material and a second layer that includes a solvent susceptible material, the solvent-susceptible material being incompatible with the solvent used to coat the solvent-coated material, wherein the first layer is disposed between the second layer and the donor substrate. Next, the thermal transfer layer of the donor is placed proximate a receptor and the multicomponent transfer layer is selectively thermally transferred from the donor element to the receptor. At least one of the solvent-coated material and the solvent-susceptible material is an organic electroluminescent material, an organic conductor, or an organic semiconductor.
In still another aspect, the present invention provides a method for patterning materials that includes the steps of thermally transferring selected portions of a first transfer layer from a first donor element to a receptor, the first transfer layer containing a first material, the first material being solution-coated from a solvent onto the first donor, and thermally transferring selected portions of a second transfer layer from a second donor element to the receptor, the second transfer layer containing a second material, the second material being incompatible with the solvent. At least one of the first and second materials is an organic electroluminescent material, an organic conductor, or an organic semiconductor.
In yet another aspect, the present invention provides a method for making a thermal transfer donor element, which method includes forming a donor element that has a donor substrate and a transfer layer, the transfer layer being formed by (a) solution coating a first material using a solvent, (b) drying the first material to substantially remove the solvent, and (c) depositing a second material such that the first material is disposed between the donor substrate and the second material, the second material being incompatible with the solvent used to coat the first material.
In another aspect, the present invention provides an organic electroluminescent display that includes a first organic electroluminescent device disposed on a display substrate, the first organic electroluminescent device having an emitter layer that is a light emitting polymer, and a second organic electroluminescent device disposed on the display substrate, the second organic electroluminescent device having an emitter layer that is an organic small molecule material.
In another aspect, the present invention provides an organic electroluminescent display that includes an organic electroluminescent device disposed on a display substrates, the organic electroluminescent device including, in the following order from the substrate, a first electrode, a small molecule charge transport layer, a polymer emitter layer, and a second electrode.
The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and the detailed description which follow more particularly exemplify these embodiments.
It should be understood that by specifying an order in the present document (e.g., order of steps to be performed, order of layers on a substrate, etc.), it is not meant to preclude intermediates between the items specified, as long as the items appear in the order as specified.